FAQ: AT&T Wireless GPRS/data/email (GSM) options (as of 6/02) explained
(obsolete)

Copyright 2002 John Navas, All Rights Reserved.
Permission is granted to copy for private non-commercial use only.

Posted as <http://attwireless.navasgroup.com/gsm_data.htm>. 

NOTE: This information was compiled by the author and is provided as a public service. The author has no connection to AT&T Wireless or Ericsson except as a customer. The author is not responsible for any errors or omissions, or for any consequential problems that might result. USE AT YOUR OWN RISK.

See also:

• "Device and Software Settings Wireless Internet, Wireless Internet Express, & Data Connect (WAP and ISP)"
  (requires free enrollment at the Cingular Developer Portal)
• AT&T Wireless Internet and Data Connect with unlocked Ericsson T39
• AT&T Wireless Internet Express (GPRS) with unlocked Ericsson T39
• AT&T Wireless WAP/GPRS/Data/Email setup for Sony Ericsson P800 new!
• Sony Ericsson WAP Gateway from AT&T Wireless
• Ericsson T39 Email Access over AT&T Wireless
• Power Unlocked Phone Setup for AT&T Wireless GSM Data/GPRS
• Newsgroup: alt.cellular.cingular

Email comments and suggestions to John Navas.

GSM Data Overview

GSM divides each radio channel into 8 time slots. Data speeds are determined by the speed of an individual time slot, and the number of time slots used:

CSD (Circuit Switched Data)

9.6 Kbps over a single time slot. Most GSM phones support CSD. (2G)

HSCSD (High Speed Circuit Switched Data)

Each time slot can be 9.6 or 14.4 Kbps, and multiple time slots can be combined for higher speeds, up to 38.4 and 57.6 Kbps respectively. Much less efficient than GPRS from a network standpoint, a significant drawback. (2.5G)

GPRS (General Packet Radio Service)

Each time slot can be 9.6 to 21.4 Kbps, and multiple time slots can be combined for higher data speeds, up to 171.2 Kbps (all 8 time slots), although current phones are limited to lower data speeds. In practice, GPRS data connections are usually limited to a maximum of 4 downstream time slots with 1 upstream time slot. Packet technology greatly enhances network efficiency. (2.5G)

EDGE (Enhanced Data GSM Environment)

Effectively an extension of GPRS that increases maximum time slot speed to 48 Kbps, pushing maximum combined data speed up to 384 Kbps (all 8 time slots). In trials, but not yet widely deployed. (3G)

1. what the carrier offers;
2. how the subscriber is configured by the carrier;
3. configuration of the actual access point in use; and
4. the capabilities of the phone in use.

It's a common misconception that GSM phones can make analog (dial-up) modem calls directly, but they can't. GSM is digital, and analog modems will only work over analog (AMPS) cellular. The "modem" in a GSM phone actually makes a digital connection to an IWU (Inter Working Unit) located at a carrier's Mobile Switching Center (MSC). The IWU has an analog modem bank that makes the actual dial-up modem calls. If a carrier doesn't provide an IWU, then analog modem calls are not possible.

For a good GSM data/GPRS overview, see "Internet Access by GSM & GPRS."

AT&T Wireless currently offers CSD and GPRS, but not HSCSD.  As of this writing, AT&T Wireless GPRS is limited to 1, 2, or 3 time slots (9.6, 19.2, or 28.8 Kbps), depending on access point configuration and load.

AT&T Wireless' new GSM (not TDMA) data plans, prices and options as currently listed here in California:

PCS/Cingular DataConnect

CSD (circuit-switched data) connections (not GPRS) to dial-up numbers. Not the same as the Circuit Switch Data feature described below. Charged by time: $4.99/mo plus 15/cents per minute. (Rate Plan minutes cannot be used.) Works much like a landline dial-up connection, either for an email or WAP client in the phone, or for an attached device (notebook computer, PDA, etc.). Speed limited to 9600 bps. You get two extra numbers for incoming data and fax calls. Not available with Wireless Internet Express (GPRS). Can be used to access WAP gateways other than AT&T Wireless' My Wireless Window through a dial-up ISP. No longer available for new orders.

Wireless Internet (Feature Code WI01)

WAP connections using CSD (not GPRS) to (and only to) AT&T Wireless' My Wireless Window WAP gateway. Listed on Cingular's Website at $3.99/mo, but offered for free on the new rate plans. Used to be bundled with packages of free interactive (SMS) messages, but no messages are bundled in the latest offering. Charged by time: WAP connections consume Rate Plan minutes. (The best time to use Wireless Internet is thus during Nights and Weekends.)

Wireless Internet Express at $2/mo (Feature Code WIX2)

WAP connections using GPRS to (and only to) AT&T Wireless' My Wireless Window WAP gateway. Not currently listed on Cingular's Website. Charged by data, not by time: 1 MB (1024 KB) of data (both directions) included; 3 cents/KB thereafter. (Note that partial KB are rounded up, just like voice minutes.) Cannot be used to access other WAP gateways. Cannot be used for email or data connections from either a phone client or an attached device (notebook computer, PDA, etc.). Not available with PCS/AT&T Wireless DataConnect.

Wireless Internet Express at $6.99/mo (Feature Code WXD1) and up

Not only WAP connections using GPRS to AT&T Wireless' My Wireless Window WAP gateway, but also ISP.Cingular, a general-purpose ISP connection to the Internet. (A dial-up ISP is not used, unlike DataConnect.) ISP.Cingular can be used with an email or WAP client in the phone, and with an attached device (notebook computer, PDA, etc.). Charged by data, not by time: 1 MB (1024 KB) of data (both directions) included at $6.99/mo (higher packages available); 3 cents/KB thereafter. (Note that partial KB are rounded up, just like voice minutes.) Not available with PCS/Cingular DataConnect. Can be used to access WAP gateways other than AT&T Wireless' My Wireless Window.

Circuit Switch Data (Feature Code WIXC)

CSD (circuit-switched data) connections (not GPRS) to dial-up numbers. The Cingular webpage describes it as "Data Connect" but it's not the same as the old PCS/AT&T Wireless DataConnect feature described above. Prerequisite: Wireless Internet or Wireless Internet Express. No monthly charge; connections consume Rate Plan minutes. Works much like a landline dial-up connection, either for an email or WAP client in the phone, or for an attached device (notebook computer, PDA, etc.). Speed limited to 9600 bps. You get an extra number for incoming data calls. Can be used to access WAP gateways other than AT&T Wireless' My Wireless Window through a dial-up ISP.

Interactive Messaging

SMS messages sent to/from your phone. If you don't buy a package of messages, the cost is 10 cents/message each way. (Interactive Messaging can be disabled if desired.)

Notes:

• The basic 1 MB Wireless Internet Express package seems to be comfortable for typical WAP usage--even with pretty frequent WAP, this author has only been consuming about 128 KB per week.
• You can check the type of Wireless Internet Express you have either on-line (select "Your Rate Plan") or by contacting Cingular Customer Care. Under the "Wireless Inet Xpress" Feature Package, if you don't have -isp.cingular and -GPRS (as in the portion of an on-line Rate Plan display on the right) then you will be limited to WAP connections to (and only to) AT&T Wireless' My Wireless Window WAP gateway; you must have those two items for general-purpose data connections to the Internet!
• If you have Wireless Internet Express (GPRS), it is probably more cost effective to send an interactive message from Email/IM on AT&T Wireless' My Wireless Window rather than directly from your phone. Session data traffic is charged against your data allowance, but there is no SMS message charge. This is likewise probably the most cost-effective (and practical) way to handle email.
• If you have a large number of Night and Weekend Minutes, it is probably more cost effective to use Wireless Internet rather than Wireless Internet Express (GPRS) on Nights and Weekends, since that is charged against your minutes rather than your data allowance. (You may need the Circuit Switch Data feature to do this.)
• As a security/anti-spam measure, some ISPs will only allow you to access your email from their own networks, and many ISPs will only allow you to send email from their own networks. In such cases, you may not be able to send/receive email with your ISP using ISP.Cingular. Check with your ISP.
• For information on how to use the email client in an Ericsson phone, see "Ericsson T39 Email Access over AT&T Wireless".
• For information on how to fax over PCS/AT&T Wireless DataConnect, see "Fax over a GSM Cellular Phone".

		If you're a mariner, a cool thing to do with WAP is get current marine weather and tide/current/wind information on your WAP-enabled cell phone! See "Weather, Tide & Wind by Cell Phone" (part of "Navas' Sailing & Racing in the San Francisco Bay Area").

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